The present invention generally relates to the devices of the type represented by automatically tripped safety valves used in gas distribution systems. More particularly, the invention relates to a safety device inserted in a fluid pipe of minimum cross-sectional area determined in order to protect it from an excess flow of the fluid flowing therein from upstream to downstream, this device comprising:
a tube exhibiting open upstream and downstream ends offering the fluid a central flow path,
retention means for holding this device in place within the pipe,
control means for controlling the fluid circulation, including a central valve and an elastically deformable annular shutter and fastened to the outer periphery of the tube, and
a hollow body fastened to the tube in the extension and upstream from this tube,
The retention means including a first set of clamps, each one of which exhibits a free end biased by an elastic force towards a radial unfolding configuration equivalent to that of the spokes of an open umbrella, and this device moves between a resting configuration, which it adopts in the event of normal fluid flow and wherein the central valve frees the central flow path, and a safety configuration, which it adopts in the event of an excessive fluid flow and wherein the central valve shuts-off the central flow path.
A device fitting this generic definition is particularly known to those skilled in the art from U.S. Pat. No. 6,962,165. Some fluid distribution systems require special safety measures, imposed by the nature of the transported fluid and by any possible risk of damage occurring to the ducts which constitute these systems. For example, the gas distribution systems in urban areas usually lie under roads and pavements, that is, under public land structures, likely to undergo various works, notably earthworks. However, if a gas duct is accidentally pulled up or severed during such works, the immediately resulting gas leak creates a high risk of fire or explosion.
In this context, safety valves have been developed to shut-off the gas ducts as soon as an abnormally high flow of gas is detected therein. However, to date, the safety valves can only be easily mounted onto new systems in the process of being laid, or possibly onto existent systems, but only during their renovation. In fact, as the ducts of the existing systems may have been constructed at different periods and according to different standards, meaning that they do not necessarily have very precisely defined diameters and exhibit, obstacles, flashes, buckles, restrictions, and/or varied bend radiuses along their run, the implementation of a safety valve in an existent system remains a tricky job. Thus, although the valve described in the aforementioned U.S. Pat. No. 6,962,165 has been designed to make such operation possible, its specific design limits its application to systems exhibiting relatively high bend radiuses.
Designed in this context, the object of the invention is hence to propose a safety device liable to be set up without excavation, in most known systems including in systems exhibiting low bend radiuses, for example of about ten times the diameter of the pipe wherein this device is introduced. To this end, the device of the invention, which still further conforms to the generic definition given in the preamble above, is substantially characterized in that each one of the clamps exhibits a tied end fastened to the periphery of the tube upstream from the annular shutter, and in that these clamps selectively exhibit, under the application of a radial compression, a folded configuration wherein their respective free ends are turned towards this annular shutter. Preferably, the annular shutter comprises a seal made in an elastomeric material whereof a downstream end is fastened to the tube, this seal exhibiting a rotational symmetry, an at least partially conical axial cross-section, and a concavity turned upstream. Furthermore, it is judicious that the seal of the annular shutter be provided such that it selectively exhibits, under the application of a radial compression, a total diameter less than that of the determined minimal cross-sectional area of the pipe, and the absence of stress, a total diameter higher than that of the determined minimal cross-sectional area of the pipe.
In order to optimize the tightness of the device, the seal of the annular shutter may be advantageously edged with a substantially cylindrical lip coaxial to the tube. Furthermore, in order to prevent the reversal of the seal, the annular shutter may comprise a retention ring reinforcing the downstream end of the seal and holding it on the tube. In an effective embodiment of the invention, the retention means comprise a ring tightly encircling the tube and linking together the respective tied ends of the clamps of the first set of clamps.
Furthermore, each of the clamps may exhibit, from its tied end towards its free end, a width that first decreases over the seven eighths at least of its length until it reaches a minimal value, then an increasing width starting from this minimal value. Each of these clamps may further exhibit, in the unfolding configuration, a curvature that moves it away from the tube at an increasing distance from its tied end. In addition to the first set of clamps, the retention means may include a second set of clamps of the same constitution as the first set and shifted axially along the tube with respect to this first set, the clamps of the first and second sets being arranged in staggered rows. An optimal holding of the device in the pipe may be obtained by making the retention means from steel.